Aluminum runs lighter — so you carry more payload on every trip, and that's money straight into your pocket. Answer a few quick questions and find out exactly how much.
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The legal limit caps your total weight. Cargo you can legally carry = legal max − truck − trailer tare. A lighter trailer leaves more room for paid cargo.
But density decides if that matters. What actually loads is the smaller of: what fits by weight, and what fits by volume (box volume × density). Dense product → you "weight out" and the light trailer wins. Light product → you "cube out" and volume is the limit.
Trips per day are derived, not assumed. Round-trip time = distance × 2 ÷ road speed + load/unload time; trips/day = driving hours ÷ round-trip time, rounded down to whole trips. Change the distance, daily hours, road speed or load/unload time and the trips update.
Then it's just money: tons × $/ton × trips/day × working days/year. The advantage line is the extra tons a lighter trailer carries, turned into dollars over a year and three years.